Demand for portable electronic devices is increasing each year. Example portable electronic devices include: laptop computers, personal data assistants (PDAs), cellular telephones, and electronic pagers. Portable electronic devices place high importance on total weight and size of the device.
The demand for higher speed circuits with smaller form factors is increasing, largely as a result of increases in the need for portable electronic devices. The density of circuits (board level, hybrid, and/or integrated circuit) is increasing as a consequence of the need for smaller form factors in the portable devices. The increased density of the circuits results in special requirements for packaging and heat dissipation.
In some instances, an external interface to the IC is required for configuration and/or control. A typical IC interface includes a parallel bus that uses several pins. In a parallel bus solution, each pin corresponds to a different bit of a digital control word. Another typical IC interface includes a serial bus that uses two pins. In a serial bus solution, one pin corresponds to a clock signal, while the other pin corresponds to the serial bit stream that provides the control word to the IC for configuration and/or control. Serial pin interfaces often result in considerably more circuitry when compared to a parallel interface. The additional circuitry in the serial pin interface consumes additional “die-area” in the IC, which may increase risk and failure rates of the interface.
Portable applications may require special small form factors that adversely impact the number of available pins in the packaging for an external interface. In integrated circuit components (ICs), bonding pads are required on the die for connection to the external pin. Often times, the bonding pads on the die take up a substantial amount of area on the die such that the die area is said to be “pad limited”. Modern technologies such as micro-SMD, and flip-chip suffer from pad limited die areas such that the number of available pins are a determining factor for the total area of the die, and hence a dominant factor in cost. The reduced available die area may adversely impact the number of available pins for the external control interface.